A compensated dual-band SPDT switch for radar duplexers at S- and X-band

A single-pole double-throw (SPDT) switch for a dual-band radar duplexer at S- and X-band is presented. The switch is particularly useful for monostatic phased array radars where a high isolation between transmitter and receiver is necessary. It consists of three PIN-diodes and needs only one switching voltage. A high isolation and a low insertion loss combined with the potential for a high power handling capability are achieved by utilizing an asymmetric PIN-diode network with shunt diodes in the transmit and a series diode in the receive path. The isolation is improved at both frequency bands by compensating the parasitic capacitance of the series diode. Simulation and measurement results are presented. The fabricated switch exhibits an isolation of more than 30 dB and an insertion loss of less than 1.4 dB in the transmit case.